The principle for a line array detector to line scan and acquire an image is that an X-ray source is driven by a mechanical scanning device to move in phase with the detector to perform X-ray scan on a person or object to be detected. Each time the mechanical scanning device moves by a unit distance (e.g., 0.2 mm), the detector acquires a line of X-ray image data. If the mechanical scanning device moves by a distance of 40 cm successively and uniformly, the detector acquires 2000 lines of X-ray image data accordingly. The data are processed by a computer to form a frame of an X-ray image of approximately 40 cm×40 cm for the object which is mechanically scanned.
An existing line array detector is structured as illustrated in FIG. 1, and comprises an X-ray probe, a signal acquisition circuit, and a low voltage power source combination. Wherein, the X-ray probe and the signal acquisition circuit are packed together in a cuboid aluminum alloy box, and the low voltage power source combination (not shown) is packet separately in a metal square box with good heat dissipation character. Wherein, the X-ray probe includes four parts of a collimator 101, a scintillator 102, an array of photosensors 103, and a shift amplifier 104. The signal acquisition circuit 100 includes an analog signal processor 105, an analog/digital converter (A/D converter) 106, and an interface circuit 107. A physical process of acquiring a line of X-ray signals includes: projecting X-rays onto the collimator 101 of the detector through the person (object) to be detected and collimated X-rays arriving at the scintillator 102; the scintillator 102 converting X-rays into visible light which are then received and converted by the photosensors 103 into electric signals; acquiring the electric signals by the back-end signal acquisition circuit 100; converting the electric signals into digital signals sequentially through the analog signal processor and preamplifier 105 and the A/D converter 106; storing the digital signals into a buffer; transmitting the image data stored in the buffer to a computer via the communication interface circuit 107; upon receiving sufficient lines of X-ray image information, the computer performing data reconstruction on the image data to form integral image data and storing the image data in a hard disk.
In an existing line array detector, due to the compact integral incorporation of the scintillator 102, the array of photosensors 103, and the shift amplifier 104, such a structure has a significant drawback in that X-rays transmitting through the scintillator directly irradiate the photosensors 103 and integrated circuit behind them, and thus cause etch damage to the integrated circuits. Therefore, the photosensors and the integrated circuits behind them tend to be damaged after a period of use or upon irradiated by a large dose of X-rays.